Network: Add an IPv4 configuration option. Hardcoded to =y for now, but I would like to be able to select IPv4 and/or IPv6 in the future

net/Kconfig

@@ -183,6 +183,13 @@ endmenu # Data link support
 
 source "net/socket/Kconfig"
 source "net/netdev/Kconfig"
+
+#source "net/ipv4/Kconfig"
+
+config NET_IPv4
+	bool
+	default y
+
 source "net/ipv6/Kconfig"
 source "net/pkt/Kconfig"
 source "net/tcp/Kconfig"

net/arp/Kconfig

@@ -8,7 +8,7 @@ menu "ARP Configuration"
 config NET_ARP
 	bool
 	default y
-	depends on NET_ETHERNET
+	depends on NET_ETHERNET && NET_IPv4
 	---help---
 		This setting is currently overridden by logic in include/nuttx/net